Mono-hybrid Crosses

Mono-hybrid crossing is a crossing, forwhich is characteristic of the difference between parental forms from each other in the available one pair of alternative, contrasting features. A sign is any feature of the body, any of its properties or quality, according to which it is possible to distinguish individuals. In plants, such a property is, for example, the shape of the corolla (asymmetric or symmetrical), its color (white or purple), etc. Characteristics include the rate of ripening (late ripeness or early ripeness), as well as resistance or susceptibility to certain diseases .

All properties in the aggregate, starting with external andending with certain features in the functioning or structure of cells, organs, tissues, are called the phenotype. This concept can also be used in relation to one of the available alternative signs.

The manifestation of properties and attributes is carried out under the control of existing hereditary factors - in other words, genes. Together, genes form a genotype.

The mono-hybrid Mendel cross is representedcrossing peas. In this case, there are such well-marked alternative properties as white and purple flowers, green and yellow color of immature beans, wrinkled and smooth surface of seeds and others.

Conducting a mono-hybrid cross, G. Mendel, an Austrian botanist of the 10th century, found out that in the first generation (F1), all hybrid plants had flowers of a purple hue, while a white color did not appear. Thus, Mendel's first law on the uniformity of the first-generation models was derived. In addition, the scientist established that in the first generation all samples were homogeneous and for all seven traits studied by them.

Thus, mono-hybrid crossessuggests for individuals of the first generation the presence of alternative signs of only one parent, while the properties of the other parent seem to disappear. The predominance of properties G. Mendel called dominance, and the signs themselves are dominant. The scientist called non-manifested qualities recessive.

Conducting a mono-hybrid cross, G. Mendel subjected self-pollinated hybrids of the first generation. Formed in them seeds the scientist sowed again. As a result, he received the following second generation (F2) hybrids. In the obtained samples, cleavage was observed according to alternative characteristics in an approximate ratio of 3: 1. In other words, three-fourths of the second generation had dominant properties, and one quarter were recessive. As a result of these experiments, G. Mendel concluded that the recessive trait in the samples was suppressed, but did not disappear, appearing in the second generation. This generalization was called "Splitting law" (Mendel's second law).

Further monohybrid crossing of a scientistconducted to determine how the inheritance will occur in the third, fourth and subsequent generations. He grew the samples using self-pollination. As a result of the experiments, it was found that plants, the characteristics of which are recessive (white flowers, for example), reproduce in posterity only with these (recessive) properties.

Several differently behaved plants of the secondgeneration, whose properties were called G. Mendel dominant (owners, for example, purple flowers). Among these samples, the scientist, analyzing the offspring, identified two groups with absolute external differences for each specific feature.

For individuals that differ in two features, a dihybrid cross is used. The tasks for determining genotypes and phenotypes are comparatively simple, when they are solved, Mendel's laws are applied.